Answer: It will take him 1 hour and 30 minutes, or 1 and a half hours to finish 24 math problems. Another solution could be 1.5 hours!
Step-by-step explanation: We know he can finish 12 math problems in 45 minutes.
To find how many minutes it takes him to complete 24 math problems, simply multiply, 12 x 2 and 45 x 2.
12 x 2 = 24 total math problems.
45 x 2 = 90 Minutes.
90 minutes can also be written as 1 hour and 30 minutes, or 1 and a half hours. That is your answer!